So called "reefer containers" or refrigerated insulated intermodule containers, which may form parts of trailers, are well known. Generally, areas between the inner and outer surfaces of the roof and side walls of the reefer form cavities to receive foaming material which provides the insulation. The foaming material may comprise liquid chemicals which react to form a quasisolid mass of air cells.
During the foaming operation, the inner and outer surfaces of the roof and side walls of the container must be shored. The shoring elements comprise platens or other restraining devices used to prevent bulging of the container surfaces during expansion of the foaming material which is inserted into the cavities under very high pressures.
The shoring elements or platens generally comprise sheets of rigid material such as plywood sheets which cover wide areas to provide pressure or resistance to prevent expansion of the surfaces of the container being contacted. Holes in the reefer unit container are adapted to be connected to discharge tubes of the foam chemical metering head to receive the foaming material under high pressure.
One present arrangement of shoring involves the installation of internal shoring elements by a group of workers who install the shoring equipment into the unit or container. The shoring equipment may comprise a series of 3/4" plywood panels approximately 4' wide and 71/2' high which provide the side panel platens which are aligned to match mounting holes with the vertical structural members inside the side wall of the containers. The platens are then fastened to the structural members by drilling holes and running screws through the platens into the structural member. Each platen may fasten to three vertical members. Ceiling platens are installed by raising them to position and supporting them with mechanical jack rods adjusted to exert sufficient tension to brace them from the floor to the ceiling without deflecting the ceiling panel.
The rear doors are shored by a sandwich device which combines a structural iron frame with platens attached. The sandwich is placed on each door and fastened to provide restraint to both interior and exterior door surface. The container of the unit with the interior shoring equipment is then moved to the foaming station. At this position, the external roof platen is lowered from overhead suspension and external side shoring section is applied. The container or unit is then foamed by moving the metering head from one end of the container to the other, successively inserting the discharge hose in the foam hole at each cavity, allowing the predetermined quantity of chemical to enter the cavity, then moving to the next hole. Each segment of the body is foamed completely, then the next segment, with the floor being formed first, then one side panel and rear door, then roof, then second side panel.
After foaming, the roof platen is raised and external forward side panel shoring is removed and moved to another station where the internal shoring is removed.
The total process as described is quite disjointed due to the distance between the shoring, foaming and deshoring positions. It further induces high labor costs due to the nature of the internal shoring and the time required for its positioning, installation and subsequent removal.
In other shoring arrangements, the internal and external shoring equipment is at one station with the walls of the container being moved between the internal and external platens before the shoring equipment is actuated to apply the required pressures or resistances. The main disadvantage of this arrangement is that the internal shoring equipment must be held in a fixed cantilever type suspension which requires a great amount of support at one end. This causes stresses to be built up in the equipment. It also causes misalignment problems which result from the sagging of the internal shoring parts.